Genomic Imprinting
3 important questions on Genomic Imprinting
Where do imprinted gene lie, what happens to them in germ cells and gametes?
Often near differentially-methylated regions (DMRs) or imprinting control regions (ICRs)
- high frequency of CpG dinucleotides, but share little sequence homology
- tandemly repeated elements, which trigger de novo methylation
Germ cell formation: imprints erased, re-established in haploid gametes; global demethylation leads to de novo methylation by Dnmt3a and Dnmt3L (co-factor)
How can you differentiate between maternal and paternal DMRs in the germline?
Maternal DMRs: coincide with transcription units
Paternal DMRs: lie within intergenetic regions
What is the role of imprinting in disease?
- Beckwith-Wiedemann syndrome (BWS): loss-of-imprinting (LOI) disease; overgrowth syndrome, activation of IGF2, risk of cancers
- Angelman-syndrome (AS): deletion/inaction of genes on maternal chromosome 15, while paternal chromosome 15 genes are imprinted and therefore silenced. Happy behaviour.
- Prader-Willi syndrome (PWS): mutation of paternal chromosome 15 genes (deletion/inactivation), while maternal genes are imprinted and silenced. Hypotonia, obesity by appetite, short, small hands and feet.
The question on the page originate from the summary of the following study material:
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